Arc-lamp electrode.



MICHAEL DOETSCH, OF NUREMIBERG, GERMANY,

ASSIGNOR TO C. CONRADTY, FABRIK ELEKTRISGHER UND GALVANISCHER KOHLEN, OF N UREMBERG, GERMANY.

I ARC-LAMP ELECTRODE.

No Drawing.

To all whom it may concern.-

Be it known that I, MIGiiAEL DOETSCH, subject of the German Emperor, residing at Nuremberg, in the Empire of Germany, have invented certain new and useful Improvements in Arc-Lamp Electrodes, of which the following is a specification.

The arc-lamp electrodes in which a mixture of chemicals is applied to the surface of the carbons, have been much used in recent years but they all show the disadvantage that the coating does not adhere firmly. It has been attempted to overcome this disadvantage by special configurations of the surface of the carbon, for example by making the carbons starshaped, or by employing grooves, radial projections, beads with thickened ends, dove-tail insertions, curved arms, or screw threads, etc. However, none of these devices have prevented the chemicals from crumbling off. Nor was success attained by the use of suitable binding agents such as dextrin, tragacanth, etc., and these substances caused considerable disturbances while the arc was passing. It is true that by selecting the correct binding agent the coating adheres better to the carbon, but owing to the crumbling which occurs when the arc is passing the connection between the carbon and the chemicals is again broken.

According to the present invention these disadvantages are overcome by roughening the carbon either during or after the process of manufacture. This can be done in many different ways, for example by employing a suitable arrangement in the press which acts upon the mass while still soft, or by mechanically working the finished carbons, by the use of a sand blast, etc.

Carbons which have been roughened in this manner not only assist the chemicals to adhere more firmly but they also considerably facilitate steady burning. This phenomenon is a very important advantage of carbons prepared in the above described manner; it manifests itself in that the mol- Specification of Letters Patent.

Patented June 13, 1916.

Application filed December 17, 1913. Serial N 0. 807,360.

ten chemicals are drawn or sucked up so that the arc is continually fedby a fresh supply. The roughening of the carbon favors the adhesion of the liquid mass in the recesses of .the carbons.

It might appear obvious to employ carbons of high porosity which perhaps might render somewhat better adhesion possible and at the same time cause the liquid chemicals to be sucked up. When working in this way however it has been found that there is the great disadvantage that the carbon, which at the arc end is quite saturated with chemicals, burns very unsteadily and that pieces fall off in a short time; this is due to the unequal expansion Within the pores passing through the carbon. The phenomenon by which the molten mass is drawn upward only occurs incompletely in porous and in quite smooth carbons.

For the sake of brevity I shall employ the Word chemicals ering those bodies applied to are lamp carbons in the above described manner for the purpose of increasing the luminosity and for imparting a pleasing or desired color.

I declare that what I claim is in the claims as cov-- 1. An arc lamp electrode consistin of a 7 carbon having a coarse and superficially porous surface to WhlCh surface is applied a mixture of chemicals.

'2. An are lamp electrode consisting of-a electrodes which consists in causing a coating of chemicals to adhere to a carbon which is only superficially porous and has a roughened surface. v

(i. The process of manufacturing are lamp electrodes which comprises roughening the surface of a substantially non-porous carbon and causing a coating of chemicals to adhere to said surface.

7. The process of manufacturing are lamp 

